The ATP-binding cassette (ABC) transporters compose one of the largest and most important families of transmembrane proteins in the biological kingdom. Within the ABC family is a group of molecules that are referred to as A class transporters that share substantial sequence similarity. The ABCA class molecules comprise twelve proteins of which only two, ABCA1 and ABCA4, have a clearly defined function. This grant proposes to generate homologous recombinant mice lacking each of the other ten A class ABCA transporters and to characterize the resulting functional deficit in the homologous recombinant mice. A novel recombinant bacterial artificial chromosome technology will be used to produce the targeting vectors and fluorescence-in-situ hybridization will be utilized to identify correctly targeted embryonal stem cell clones. Characterization of the null mice will employ high-throughput technologies including liquid chromatography mass spectrometry analysis of tissue lipids and spotted oligonucleotide microarray measurements of gene expression. All of the reagents generated in this work, including null mice, full-length expression cDNAs, and anti-ABCA1 antibodies will be made available to the research community so that other investigators can exploit them in order to facilitate our understanding of the role these ABCA transporters play in human physiology and disease.